Essential Sound

Wednesday, March 31, 2010

Bryston has been making high-quality amplifiers, preamps and other audio gear since the 1980s. It has been successful in taking on the ultra-high-end with products that are less expensive, but often just as satisfying in their audio quality and feature set.

In the 1990s, I was a big fan of the BP-20 preamp, and in early 2003, I purchased a Bryston 14B-SSTII 600-wpc power amp that was ideal for audiophiles and recording studio engineers who wanted a powerful, transparent, solid state amp that matched well with any speaker. And considering how good it sounded for $6,000, more expensive boutique amps really did not buy you better sound.

Bryston has reached a similar perch with its BDA-1 digital-to-analog converter (DAC). It is not that expensive, at under $2,000, and its combination of analog/digital parts selection, full feature set and high-end audio performance may be all you need in a rack-mount converter.

Features

Priced at $2,150, the made-in-Canada BDA-1 is a full-rack space sized DAC with the Bryston sonic pedigree and a host of features that make it quite a value. The unit features a switchable upsampling circuit, eight separate inputs including USB, balanced/unbalanced outputs, and separate sample rate indicator LEDs.

The BDA-1’s converter section consists of a dual-192-kHz, 24-bit CRYSTAL converter (CS-4398). The converter operates synchronously — even in the upsampling mode (176 or 192 kHz, depending on source frequency). The analog section is fully balanced and Class A. The digital and analog sections each sport their own isolated power supplies.

Overall, the Bryston BDA-1 is exactly what I expected from the innovative, yet common-sense Canadian audio manufacturer. A well-designed, excellent sounding DAC with plenty of inputs and outputs. You throw in the switchable upsampling to open up old 16-bit recordings and the informative sample rate status lights, and you got yourself one nice DAC.

The BDA-1’s eight digital inputs include: four RCA coaxial SPDIF jacks, a USB jack for taking digital audio from a computer, two TOSLink ports and an AES-EBU standard XLR jack. A digital SPIDIF bypass jack outputs the native input signal without any conversion or processing. Good for those who use DVD players, but only have one digital SPDIF output. The analog output section consists of a set of unbalanced RCA jacks and a pair of fully balanced XLRs.

The unit can be operated by an optional remote control and has the capability to update its internal software from a network — via its built-in RS-232 port. It is also 12-volt triggerable for a fixed installation.

The front-panel push buttons include controls for the eight individual input selections, upsampling and power. The BDA-1’s front panel also is equipped with the converters handiest feature — a sample rate status display. It has LEDS for 32 kHz, 44.1 kHz, 48 kHz, 88.2 kHz, 176 kHz and 192 kHz, as well as Digital Lock.

As someone who works with a variety of components and audio with different sample rates, it is so convenient to instantly know the incoming sample rate. Many popular converters do not contain this feature, including my Benchmark DAC1 Pre. (The Lavry DA-10 and DA-11 do indicate sample rate status to 96 kHz).

Sample rate indicators are extremely useful for figuring out computer audio sample rates. Computers often have multiple sample rate setting adjustments that have to be reconciled between software and hardware adjustments. Having visual sample rate confirmation via the outboard DAC is a good thing, so that you actually know what the computer is spitting out.

There is nary a feature missing from the BDA-1, except for a headphone amp. Today, they are so common place in the audiophile half-rack DACs that when I see a DAC without one, I feel lost. Or at least my headphones do.

Inside the BDA-1

According to the Bryston design division, the BDA-1 design was an endeavor to offer as transparent and jitter-free conversion as possible. The designers favored synchronous conversion, which bucks the recent trend of asynchronous conversion used in many DACs.

Synchronous conversion uses decimation (A/D) and interpolation (D/A) filters to process digital signals. Asynchronous converters use decimation and interpolation as well, but also rely on a primary sample rate converter that converts any incoming sampling frequency (32 Hz to 192 kHz) to a fixed sample frequency.

The claim is that asynchronous conversion reduces clock jitter to the point where it has no negative effect on the audio, and that high-resolution ASRC processing introduces no audible noise or distortion (the claimed processing THD+N is typically -150 dB).

According to Bryston, the advantage of this synchronous upsampling process is better processing of the upsampled signal by the DAC chip. Additional noise-shaping is said to “shift” audio band noise to the inaudible frequencies. Another advantage of this upsampling process is that a totally new clock signal is applied, which is claimed to significantly reduce jitter.

Proponents of synchronous converters say that asynchronous converters are tampering with bit transparency by always running an incoming digital signal through the sample rate converter. Synchronous converter designers also assert that with careful design, their products yield excellent jitter and noise performance as well. Judging by my evaluations with both types of converters, you can still have sonically accurate, grit-free sound with either asynchronous or synchronous — if the engineers utilize good, careful design and parts implementation.

BDA-1 converter design

Bryston uses two independent DAC chips in the BDA-1: the CRYSTAL CS-4398. The CS-4398 is a hybrid, multi-bit, delta-sigma DAC. This chip uses several methods to optimize the conversion process.

This DAC oversamples the incoming signal in one of three oversampling modes, based on the input sample rate. The single-speed mode supports input sample rates up to 50 kHz and uses a 128x oversampling ratio. The double-speed mode supports input sample rates up to 100 kHz and uses an oversampling ratio of 64x. The quad-speed mode supports input sample rates up to 200 kHz and uses an oversampling ratio of 32x, with a very low-jitter clock. This design, according to Bryston, allows for filtering noise far above the audible range with no loss of transparency.

The BDA also contains a synchronous “upsampling” circuit that can be turned on or off. This feature converts the native digital signal from one sample rate and bit depth to another. With upsampling engaged, sample rates of 32 kHz, 48 kHz and 96 kHz signals are upsampled to 192 kHz. The 44.1 kHz and 88.2 kHz signals are upsampled to 176.4 kHz. The 16-bit word length is processed to 24-bits. The additional eight bits are filled with “placeholder” information.

A Bryston technical paper says the upsampling process doesn’t add any new data to the audio signal, but instead it puts the data in a form which can better be used by the DAC, resulting in a sonic presentation that is slightly more expansive than the non-upsampled mode. This sonic benefit, of course, depends on the audio feed to the converter.

According to Bryston, the advantage of this synchronous upsampling process is better processing of the upsampled signal by the DAC chip. Additional noise-shaping is said to “shift” audio band noise to the inaudible frequencies. Another advantage of this upsampling process is that a totally new clock signal is applied, which is claimed to significantly reduce jitter. (and the jitter is quite low according to our bench test — Ed.)

The BDA-1‘s analog side of the equation includes the use of discrete balanced components, including audiophile grade op-amps, capacitors and resistors that all of us audiophiles come to expect in well designed high-end gear.

The setup

I used the Bryston BDA-1 in two different setups: in my audiophile rack and in my recording rack. In the audiophile installation, I linked various DVD-A/CD/BD players to the DAC, including an Oppo BDP-83SE, Lexicon BD-30, Esoteric DV-50, and a Yamaha DVD-2300 Mark II; a Macbook Pro was used for USB output. Other DACs I had on hand for comparison included the internal DACs of the aforementioned players and a Benchmark Media DAC1-Pre, Lavry DA10 and a Mytek 24/96. I also threw in a couple of 1990s CD players just to hear how far converter technology has progressed.

On the Yes — Fragile DVD-A, the Steve Howe played “Mood for a Day” classical guitar piece sounded amazingly accurate with its crisp fingerpicking, which was mic’d in stereo during the original early ‘70s recording sessions. It is a great track to check out converters — so natural and analog sounding.

The DACs were all connected to my Coda Preamp using Alpha-Core or Westlake Low PE Distortion digital interconnects. The analog output of the Coda fed my Pass Labs X350.5 power amp, which drove Legacy Focus 20/20 speakers. Preamp and speaker cables were Alpha-Core solid-silver, and all components were linked to wall power via ESP Pro AC cables.

I listened to a variety of music types, mostly commercial 24-bit/96 kHz sampling DVD-As with a few 192 kHz and 88.2 recordings thrown in. I also listened to some well-mastered CDs and my own 24-bit/96 kHz acoustic guitar recordings.

My initial notes from long-term listening revealed the BDA-1 as a wonderfully detailed, yet not overly-analytical DAC. Its musical smoothness made highly-modulated instruments, such as trumpet, saxophone, trombone and loud drum cymbals sound more analog-like. I really liked hearing the drum cymbal hits with their metallic naturalness but without being thin and artificial — like the converters in my old 1990s CD players.

The Bryston’s stereo imaging was wide, with plenty of depth, although I thought the Benchmark had slightly more front-to-back separation of instruments (more apparent with headphone listening). The bass was accurate with a tightness and speed that matched any other top-quality DAC that I have used.

On the the Eagles — Hotel California DVD-A, the Randy Meisner song, “Try and Love Again,” stood out with nicely separated acoustic and electric guitars, and drum cymbals getting full separation in the mix, as they should through a high-end DAC.

On the Yes — Fragile DVD-A, the Steve Howe played “Mood for a Day” classical guitar piece sounded amazingly accurate with its crisp fingerpicking, which was mic’d in stereo during the original early ‘70s recording sessions. It is a great track to check out converters — so natural and analog sounding.

I sampled the Lawrence Juber — Guitar Noir, a high-res 24/96 DVD-A from AIX Records. The title cut is a nice demo for percussion and acoustic guitar with wide expansive soundfield and resolution galore. I have heard this recording numerous time on a variety of converters. The Bryston handled it just fine — showcasing a realistic sheen on the percussion and the open airiness around the individual string picking of Mr. Juber. The overall timbre was accurate without being too forward or thin. As Goldilocks said, ‘just right.”

The Beck — Seachange 24-bit, 88.1 kHz DVD-A contains a number of acoustic guitar-based songs with electronic accompaniment and bass and drums. The disc is wonderfully warm, yet percussive, with good instrument separation. The BDA-1 relayed the DVD-A in a convincing fashion. The songs “Golden Age,” “Guess I’m Doing Fine” and “Lost Cause” are standouts musically, lyrically and sonically, and the BDA-1 helps convey how good these recordings are.

In comparison to the Lavry, Mytek and Benchmark, I thought the Bryston was the least forward in the upper midrange and lower treble. Its ultra-smooth character made it quite musical, shall I dare say it again, analog-like. The trade-off may be an impression of a reserved high-end, but that impression is more psycho-acoustic due to its smooth character. Our bench measurements indicate the BDA-1 has an extended top-end in the audible and inaudible portions of the spectrum.

(Editor's Note: These different sonic impressions of the DACs were made from carefully, repeatedly matched level comparisons via the headphone amp. Through speakers, it was more difficult to detect the subtle differences when listening one on one).

The Bryston’s smoothness also was apparent on the Fleetwood Mac — Rumours DVD-A, which has quite a bit of high-end EQ. On some converters, it can sound edgy and bright, but on the Bryston, it sounded fairly smooth, but did not filter out the bright character. With its ability to smooth out digital audio’s rough edges, I believe this is an ideal converter for those with vast CD collections and discs dating back to the early years of the medium — when digital sound was rough edged.

I played around quite a bit with the “upsampling” feature. I love the capability of switching it in or out to make comparisons. Overall, it does what I have found in most DAC upsamplers: the process can subtly open up the transient edges. The sound becomes a bit more present and wider.

I think the upsampler works best with old, slightly dark 16-bit PCM recordings. I played a number of of CBS Living Stereo classical CDs through the upsampler, and was quite pleased with the slight sense of increased space and a bit more energy in the treble over the non-processed recording.

On music with abundant treble energy, like ‘80s pop dance music CDs (Madonna — Immaculate Collection, for example), it made the cuts seem a bit too forward — an edginess that I did not like. Its usefulness really depends on the source, but it is nice to have it as a tool.

For the pros

Those who work in the professional realm, or audiophiles who do their own recording and editing, will appreciate the BDA-1’s palette of features — as well as its sonics. I routed a number of live-to-two track, high-resolution guitar tracks from my recording rig (two Shure KSM-141 cardioid mics, True P2 Mic Preamp into a TASCAM DVRA-1000 HD hard disc recorder) and connected it to the BDA-1 via its balanced AES/EBU input.

My Martin 00-18V finger-style guitar recordings were handled with ease by the BDA-1; it's nice to hear unprocessed, live 24-bit minimalist recordings through good sounding converters, such as the Bryston, Benchmark and Lavry and Mytek. The Bryston is super quiet and recordists and engineers will like its ability to hear deep into a mix.

Pros will also appreciate the BDA-1's plethora of inputs (though only one AES/EBU XLR input). And of course, the sample rate indicators will give them instant verification of the incoming rate from the source, such as an editing computer’s sound card or a digital desk.

I played around quite a bit of with the “upsampling” feature. I love the capability of switching it in or out to make comparisons. Overall, it does what I have found in most DAC upsamplers: the process can subtly open up the transient edges. The sound becomes a bit more present and wider.

Speaking of computers, the USB brings up the review’s few minor negatives. The USB input only allows sample rates of 48 kHz and 16-bit word length input. But the competition, such as Benchmark and Lavry, now offer 96 kHz input capability via USB; me thinks it would be beneficial for Bryston to add the high-res word length/sample rate to its architecture as well

(Editor's Note: Bryston Marketing Spokesman James Tanner said the 16-48 USB input implementation was added for those who do not have a soundcard on their computer, but wanted an option to get audio from the PC to their BDA-1. Bryston believes that those who want higher-quality, high-res audio output from their computer will use a sound card’s AES/EBU or SPDIF jack to connect to the BDA-1.

"USB is only capable of 96/24, at this point, and then only with companies writing proprietary software to implement it,” Tanner said. “When USB chips become available that can do 192/24 (as all the other inputs on the BDA-1 are capable of) then we will certainly look at adding higher ‘res’ capability to the BDA-1’s USB input.” The BDA-1 can improve the sound of the 16-bit USB feed, Tanner added, by running it through the upsampling circuit, which takes it to 24-bit and 176.4 kHz sample rate).

My other BDA-1 niggle is lack of a headphone amp. Despite its in-the-rack, purist audiophile DAC underpinnings, I think the BDA-1 should have a headphone amp. Many of its competitors are doing big business with the headphone audiophiles, and with the retail price at just over $2,000, what's another a couple of hundred bucks?

The verdict

Overall, the Bryston BDA-1 is exactly what I expected from the innovative, yet common-sense Canadian audio manufacturer. It is a well-designed, excellent sounding DAC with plenty of inputs and outputs. You throw in the switchable upsampling to open up old 16-bit recordings and the informative sample rate status lights, and you got yourself one nice DAC.

Can you spell S-T-E-L-L-A-R S-O-U-N-D Award? For more information, go to Bryston BDA-1 DAC.

BENCH NOTES

Bryston BDA-1 D/A Converter

by Bascom King

The Bryston BDA-1 is a compact, versatile D/A converter that will accept input sampling frequencies from 32 Hz – 192 kHz. It is a particularly useful converter, with such features as fully-balanced operation, eight digital inputs, digital pass-thru and front panel LEDs for every sample rate.

BDA-1 measurements were made with AES/EBU input and balanced outputs. Output impedance for balanced and unbalanced outputs respectively were 143 and 72 ohms. Frequency response for the sampling frequencies of 44.1 kHz, 96 kHz, and 192 kHz is shown plotted in Figure 2. With frequencies extended down to 10 Hz, there was no roll-off at the low frequency end. With the “upsampling” mode engaged, there was a slight but inconsequential increase in the cutoff frequencies for sample rates below 176.4 kHz.

The THD+N of a 1 kHz mid-band signal vs. level, in respect to full scale, decreased rapidly from about –105 dBFS at 0 dBFS to about –115 dBFS below –5 to –10 dBFS for all sample rates.

In most PCM converters, it should be noted that noise and dynamic range measurements taken at 176 kHz or 192 kHz are typically no better — or sometimes not as good — as the measurements made at 44.1 kHz, 48 kHz or 96 kHz. This higher noise floor measurement with the highest sample rates is the result of increased out-of-band noise being generated by the DAC’s higher-frequency sample rate processing. However, this aliasing noise and the resultant filtering is so far out of the audible band that it does not have any affect on the actual sound quality versus the lower sampling frequencies. The numbers just don’t look as good.

Deviation from linearity at all three sample rates was very good, down to –120 dBFS and up to about +10 dB or less at –140 dBFS. Channel separation numbers were excellent, and the results were a surprise in that they didn’t materially decrease with frequency — as is almost always the case with this measurement. The channel-separation measurement is plotted in Figure 1 for a sample rate of 192 kHz. Green = L > R; Yellow = R > L.

Finally, in a test for jitter rejection, a 1 UI of 500 sine wave jitter was superimposed on a 1 kHz 0 dBFS test signal; the typical sidebands of 500 Hz on either side of the nulled-out 1 kHz test signal were completely absent in this test. The BDA-1 is excellent at suppressing jitter.

Overall, the BDA-1 measured well and, as important, sounded quite good in my system. A great converter and its measurements back up Mr. Gatski's subjective audiophile quality conclusions.

Bascom King is owner and chief technician for BHK Labs in Satna Barbara, Ca.

1 comment:

You mentioned the Oppo BDP-83 and Esoteric DV-70 in your review, but didn't give a comparison of how their internal DACs compared to the Bryston. I imagine many folks will be particularly interested in the BDP-83SE comparison, as its Sabre chip is getting much praise and attention.